Demand analysis and technical selection of the use and maintenance of biosafety cabinet

Bio safety cabinet Cabinets (BSCs) is a technical product that uses air purification technology to achieve physical isolation of * channels It is designed to protect the operator, laboratory environment and experimental materials when operating infectious experimental materials such as primary cultures, bacterial strains and diagnostic specimens, so as to avoid exposure to infectious aerosols and splashes that may be generated in the above operation process 。 Aerosols can be produced when operating a liquid or semifluid, such as shaking, pouring, stirring, or dropping a liquid onto a solid surface or another liquid When inoculating the agar plate, inoculating the cell culture bottle with pipette, transferring the suspension of infectious reagent to the micro culture plate with multi-channel sampler, homogenizing and vortex shaking the infectious substance, centrifuging the infectious liquid and operating the animal, these laboratory operations may produce infectious aerosol Because aerosols with a diameter less than 5 p.m and tiny droplets with a diameter of (5-1o0) Pan cannot be seen by the naked eye, laboratory workers usually do not realize that particles of this size are forming and may attract people or cross contaminate other materials on the work surface It has been shown that the correct use of biosafety cabinets can effectively reduce the laboratory infection caused by aerosol exposure and cross contamination of culture Biosafety cabinets also protect the environment 1 Basic status of biosafety cabinets before SARS in 2003, only the Ministry of agriculture, disease control center, microorganism research institutions and other institutions contacting with highly pathogenic pathogens used biosafety cabinets The biosafety cabinets used were mainly imported from Europe and America or Singapore, and there was no biosafety cabinet manufacturer in China After SARS, great attention has been paid to the use of biosafety cabinets Because of the 3rd edition of who laboratory biosafety manual, cnas-cl05-2006 laboratory biosafety accreditation criteria, WS 233-2002 general biosafety criteria for microbiological and biomedical laboratories, GB 19781-2005 / ISO 15190:2003 safety requirements for medical laboratories and GB In recent years, medical and health institutions and disease prevention and control institutions pay more and more attention to the biosafety protection facilities As the biosafety protection equipment, the demand of the biosafety cabinet is increasing At present, domestic biosafety cabinets are widely used in medical and health, disease prevention and control, medical and health care, food health and other fields and laboratory level research institutions, as well as in biopharmaceutical, environmental monitoring and scientific research institutions Today, there are about 20000 biosafety cabinets in use In the initial stage, the main solution is to fill in the gaps and meet the needs of users, but not enough attention has been paid to the safety maintenance of users of biosafety cabinets As the vast majority of manufacturers, their work focuses on production and market, and they do not carry out on-site installation inspection and maintenance inspection during use; as users, due to the lack of knowledge of product structure and protection principle, they do not have the safety protection awareness of installation acceptance and maintenance inspection during use, they think that the use of safety cabinets is safe, once and for all In fact, in order to regulate the quality of biosafety cabinet, Beijing medical device inspection institute started to formulate the standard of biosafety cabinet as early as 2004 YY 0569-2005 "biosafety cabinet" industry standard was issued in 2005 and has been formally implemented since June 1, 2006 The standard comprehensively draws on the requirements and detection methods of NSF / ANSI 49-2002 and en12469:2000 For example, the requirements of NSF / ansi49-2002 for the classification of secondary biosafety cabinets are divided into four types: A1, A2, BL and B2; the reference of EN In 12469:2000, Ki discus (potassium iodide) test method was used to detect the characteristics of personnel protection At the same time, in view of the current situation of the Chinese market, some performance requirements are put forward innovatively by reference to the two standards, such as airflow display, alarm system, three-dimensional integral forming of the working area and negative pressure design, etc.; in the standards, clear technical requirements are put forward for installation and annual maintenance inspection 2 Biological safety cabinets For many years, the basic design of the biosafety cabinet has been improved many times The main change is the addition of HEPA filter in the exhaust system For particles with a diameter of 0.3tan, HEPA filter can retain 99.9r7%, while for larger or smaller particles, it can retain 99.99% This characteristic of HEPA filter enables it to effectively intercept all known infectious factors and ensure that the air discharged from the safety cabinet is completely free of microorganisms The second improvement in the design of the biosafety cabinet is to deliver HEPA filtered air to the work surface, so as to protect the objects on the work surface from pollution This feature is usually called product protection O biosafety cabinet is a ventilation device that provides personnel protection and environmental protection in the process of microbial experiment Some types of biosafety cabinets can also provide clean local environment for the experiment to protect the experimental materials and prevent cross contamination between the experimental materials According to its structure and protection ability, the biosafety cabinet is divided into three levels: Level I biosafety cabinet, level II biosafety cabinet and level III biosafety cabinet Class I biosafety cabinet: the air inlet enters the biosafety cabinet at a low speed of not less than 0.40 M / s from the front window operation port (called inflow air flow) The air passes through the surface of the workbench and is discharged from the biosafety cabinet through the exhaust pipe to provide personnel protection The air polluted by the experiment is filtered by the filter and discharged from the laboratory to protect the laboratory environment from the pollution of microbial factors However, because the air in the laboratory directly enters the experimental operation area through the front window of the operation, the class I biosafety cabinet can not provide a clean environment for the experimental operation area, and has no function of protecting experimental materials, so it is rarely used at present Table 1 differences between class I, class II and class III biosafety cabinets note: the cabinets with horizontal and vertical air flow ("super clean workbench") are not biosafety cabinets Nor can it be applied to biosafety operations The class II biosafety cabinet is similar to the class I biosafety cabinet of the laboratory medical network It provides personnel protection through the air inlet of the front window operation port of the biosafety cabinet The air flow polluted by the experiment is filtered by the filter and then discharged into the laboratory to protect the environment from the pollution of microbial factors However, the inlet air of the window operation port does not directly enter the experimental operation area, but flows to the operation area in the form of laminar flow after being filtered by the filter on the top of the working area in the biosafety cabinet (called downdraft), which not only provides a clean environment for the experimental operation area, and makes the experimental materials free from environmental pollution, but also prevents the laminar flow from producing gas between different areas of the operation area The cross contamination of sol According to the structural characteristics and air flow mode, the class II biosafety cabinet is divided into four types: A1, A2, B1 and B2 Among them, the air flow of the A1 and A2 type biosafety cabinets is powered by a single fan in the cabinet, 70% of the air flow of the fan circulates in the cabinet, forming a downdraft, 30% of which is directly discharged to the laboratory, or discharged out of the laboratory through the sleeve type soft connection pipe This 30% air volume is supplemented by the flow of air As the exhaust channel of type A1 biosafety cabinet is positive pressure, once it occurs, the polluted air will leak into the laboratory directly, and there are structural defects Now it has been basically replaced by type A2 biosafety cabinet 30% of the air flow of B1 type biosafety cabinet circulates in the biosafety cabinet, forming a downdraft 70% of the air flow is directly discharged out of the laboratory through a fully closed hard connection pipe 70% of the air flow is supplemented by the air flow Its power mainly comes from the exhaust fan outside the laboratory The inflow and downdraft of B2 type biosafety cabinet are completely discharged out of the room by fans outside the laboratory through closed hard connecting pipes The downdraft is powered by fans inside the biosafety cabinet, and the inflow airflow is guaranteed by the air flow difference provided by two fans In terms of the protection ability to prevent microbial aerosol pollution, four types of biosafety cabinets, Al, A2, BL and B2, are the same Because the B1 and B2 biosafety cabinets directly discharge the air out of the laboratory, they show their advantages when toxic gases are produced in the process of the experiment On the one hand, toxic gas can be completely discharged from the laboratory to prevent the harm to the laboratory personnel, especially the B2 type biosafety cabinet has no gas circulation in the cabinet, and it can also avoid the gas circulation that has an impact on the experiment generated in the experiment to enter the experimental area At present, class II A2 and B2 biosafety cabinets are widely used The level III biosafety cabinet is used for the operation of microbial materials with a risk level of 4, which can provide good personal protection for Zui All interfaces of class III biosafety cabinet are "sealed", the air supply is filtered by HEPA, and the air exhaust is filtered by two HEPA filters, further improving the environmental protection The level III biosafety cabinet is controlled by an external special exhaust system to keep the interior of the cabinet under negative pressure (no less than 120 PA) Only through the sturdy rubber gloves attached to the biosafety cabinet can the hand reach the work surface The class III biosafety cabinet shall be equipped with a sterilized transfer box equipped with HEPA filter and exhaust device The class III biosafety cabinet can be connected with a double door autoclave, and it can be used to remove the pollution of all articles entering and leaving the biosafety cabinet Several glove boxes can be connected together to increase the working area Class III biosafety cabinet is applicable to laboratories with class III and class IV biosafety levels 3 The main problems existing in the use and maintenance of biosafety cabinets Biosafety cabinets have been widely used in medical and health institutions, disease prevention and control institutions, medical and health care, food hygiene fields and laboratory level research institutions, in which hospitals and research laboratories account for a large proportion Through investigation, it can be found that there are three main safety problems that directly or indirectly affect the use and maintenance of the biosafety cabinet, one is the manufacturer, the other is the user, and the third is the third-party testing agency 1) The problems of manufacturers (1) the technical foundation of manufacturers is weak The production process and technical conditions of manufacturers are uneven From the product registration and inspection, most of the production enterprises were originally engaged in the production of purification equipment, and the production of biosafety cabinets saw a broad market development prospect When the products were finalized, although the manufacturer's enterprise standard is based on YY 0569-2005 "biosafety cabinet" is formulated, but the manufacturer does not have many detection conditions such as microbial protection Generally, the products submitted for inspection and registration are difficult to pass the inspection at one time, often in the repeated state of rectification to recovery inspection, and the inspection is regarded as a verification design Moreover, because the biosafety cabinet standard is formulated by referring to NSF / ANSI 49-2002 and en 12469:2000 standards, domestic manufacturers have very limited awareness of the standard, so there are often defects in product design, which are difficult to be found without microbial protection and other related tests During the registration inspection, we also found that there are many registered biosafety cabinet products with outstanding Zui problems Even if the manufacturer who has obtained the registration certificate designs and produces the new biosafety cabinet products with new process, it will also face some technical problems, which need to be rectified The design concept of various safety performance is not